Electric heating device for hot runner systems

摘要

An electric heating unit for hot runner systems, and in particular for hot runner nozzles and/or hot runner manifolds includes at least one tubular or muff-like support and at least one heating layer fitted with heating conductor tracks. The heating layer is a fired foil or a fired thick-film paste and the muff-like support is able to be slipped onto a material feed pipe.

主权项

1. A hot runner nozzle having a cylindrical material feed pipe and an electrical heating unit, the material feed pipe comprising:
a first end and a second end; a wall; a base at the first end of the cylindrical material feed pipe; and a nozzle tip at the second end of the cylindrical material feed pipe; and the heating unit comprising: a tubular or muff-like support made of a sintered ceramic; a heating layer deposited on said ceramic support, said heating layer comprising meandering heating conductor tracks; and an outer cover layer externally covering and electrically insulating the heating conductor tracks and the tubular or muff-like support below; wherein the heating layer and the cover layer being a fired foil or a fired thick-film paste; wherein the cylindrical material feed pipe has a greater thermal expansion than the tubular or muff-like support; and further wherein in a first state before heating the tubular or muff-like su ort of the heating unit is slipped at a clearance fit with a predetermined clearance on the cylindrical material feed pipe, the clearance fit allowing the heating unit to be exchanged in the first state, the predetermined clearance being such that in a second state, which is a heated state of the heating unit, an expansion of the cylindrical material feed pipe as a result of the thermal expansion of the cylindrical material feed pipe being greater than the thermal expansion of the tubular or muff-like support achieves a direct heat transfer between the tubular or muff-like support and the cylindrical material feed pipe.